U.S. patent application number 14/477213 was filed with the patent office on 2016-03-10 for method for screening skin barrier function enhancing agent based on epidermal serine racemase and/or d-serine level, and skin barrier function evaluation method.
This patent application is currently assigned to SHISEIDO COMPANY, LTD.. The applicant listed for this patent is SHISEIDO COMPANY, LTD.. Invention is credited to Masato lino, Chieko Mizumoto, Hisashi Mori, Yosuke Tojo, Yuzo Yoshida.
Application Number | 20160069867 14/477213 |
Document ID | / |
Family ID | 55437292 |
Filed Date | 2016-03-10 |
United States Patent
Application |
20160069867 |
Kind Code |
A1 |
Tojo; Yosuke ; et
al. |
March 10, 2016 |
METHOD FOR SCREENING SKIN BARRIER FUNCTION ENHANCING AGENT BASED ON
EPIDERMAL SERINE RACEMASE AND/OR D-SERINE LEVEL, AND SKIN BARRIER
FUNCTION EVALUATION METHOD
Abstract
The object of the invention is to develop a screening method for
drugs having effects of increasing skin barrier function in in
vitro experimentation, and to evaluate skin barrier function for
skin. Serine racemase activity and/or expression level are used as
an indicator to allow screening of candidate drugs.
Inventors: |
Tojo; Yosuke; (Kanagawa,
JP) ; lino; Masato; (Kanagawa, JP) ; Mizumoto;
Chieko; (Kanagawa, JP) ; Yoshida; Yuzo;
(Kanagawa, JP) ; Mori; Hisashi; (Toyama,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHISEIDO COMPANY, LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
SHISEIDO COMPANY, LTD.
Tokyo
JP
|
Family ID: |
55437292 |
Appl. No.: |
14/477213 |
Filed: |
September 4, 2014 |
Current U.S.
Class: |
424/756 ;
424/764; 435/29; 435/6.12; 530/372 |
Current CPC
Class: |
A61K 36/899 20130101;
A61K 8/9789 20170801; C12Q 2600/136 20130101; G01N 33/5044
20130101; G01N 2333/99 20130101; A61K 38/011 20130101; G01N 2800/20
20130101; A61K 36/28 20130101; A61Q 19/00 20130101; A61K 2800/782
20130101; C12Q 1/6883 20130101; C12Q 2600/148 20130101; G01N
2333/968 20130101; G01N 33/6812 20130101; A61K 8/9794 20170801;
C12Q 2600/158 20130101; C12Q 1/6876 20130101; A61K 8/645 20130101;
A61K 36/9068 20130101; A61K 36/9068 20130101; A61K 2300/00
20130101; A61K 36/28 20130101; A61K 2300/00 20130101; A61K 36/899
20130101; A61K 2300/00 20130101 |
International
Class: |
G01N 33/50 20060101
G01N033/50; A61K 36/28 20060101 A61K036/28; A61K 36/9068 20060101
A61K036/9068; C12Q 1/68 20060101 C12Q001/68; A61K 38/01 20060101
A61K038/01 |
Claims
1. A method for screening a skin barrier function enhancing agent,
using the activity or expression level of serine racemase and/or
D-serine level in keratinocytes as an indicator.
2. The screening method according to claim 1, comprising: adding a
candidate drug to keratinocytes; measuring the activity or
expression level of serine racemase and/or the D-serine level in
the keratinocytes; and determining the skin barrier function
enhancing effect of the candidate drug based on the activity or
expression level of serine racemase and/or the D-serine level.
3. The screening method according to claim 2, further comprising a
step of inducing differentiation of the keratinocytes.
4. The screening method according to claim 3, wherein the screening
method is conducted in the differentiation-induced
keratinocytes.
5. The screening method according to claim 1, wherein the
measurement of the serine racemase expression level is carried out
by measuring the amount of serine racemase mRNA or protein.
6. The screening method according to claim 1, wherein the
measurement of serine racemase activity is carried out by measuring
the substrate conversion efficiency by serine racemase, or
measuring the amount of D-amino acid product.
7. A serine racemase activating agent comprising one or more
substances selected from the group consisting of hydrolyzed oat
protein, Lempuyang extract, and Elephantopus mollis extract as an
active ingredient, which is obtained by the screening method
according to claim 1.
8. A method for evaluating a skin barrier function, using an
activity or expression level of serine racemase and/or D-serine
level from a skin sample isolated from human skin as an
indicator.
9. The skin barrier function evaluation method according to claim
8, comprising: measuring the activity or expression level of serine
racemase and/or D-serine level in a skin sample isolated from a
subject, and determining the skin barrier function of the subject
from the activity or expression level of serine racemase and/or
D-serine level.
10. The skin barrier function evaluation method according to claim
8, wherein measurement of the serine racemase expression level is
carried out by measuring amounts of mRNA or protein of serine
racemase.
11. The method according to claim 8, wherein the measurement of
serine racemase activity is carried out by measuring the substrate
conversion efficiency or amount of D-amino acid product by serine
racemase.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for screening a
skin barrier function enhancing agent, and to a method for
evaluating a skin barrier function for skin.
BACKGROUND ART
[0002] When skin barrier function is lost, skin moisture is also
lost and infiltration of exterior foreign matter occurs, creating a
condition of sensitive and dry skin and skin roughening, and
potentially resulting in dermatitis and allergy. From the viewpoint
of developing functional foods, cosmetics and pharmaceuticals,
therefore, it is desirable to develop drugs that can increase skin
barrier function. Factors for increasing skin barrier function
include methods of increasing the amount of intercellular lipids or
arranging their orientation, and drugs such as disclosed in PTL 1
have been developed that promote production of intercellular
lipids.
[0003] Indicators for skin barrier function include transepidermal
water loss (TEWL) and the degree of penetration into skin using an
indicator substance such as a pigment. Skin TEWL can be measured
using an apparatus such as a Vapometer, but because measurement of
moisture content is an unstable indicator easily affected by the
measuring environment including atmospheric moisture content and
air flow, as well as the body temperature, mental state and
perspiration of the subject, it has been desired to devise methods
allowing more stable evaluation of skin barrier function. When the
degree of penetration of an indicator substance is to be used as
the indicator of skin barrier function, the pigment or other
indicator substance must be applied onto the skin, creating a
significant burden on the skin.
[0004] In order to perform screening of drugs with effects of
increasing skin barrier function from among numerous candidate
drugs it is possible to use TEWL as the indicator of skin barrier
function for in vivo experimentation, but this is unstable and
significantly affected by the measuring environment, and it has
been difficult to accomplish screening of drugs with an effect of
increasing the physiological and structural skin barrier function
from among numerous candidate drugs. On the other hand, such
screening methods that have been considered include methods of
using isolated skin to measure endogenous factors in skin that
contribute to recovery and enhancement of barrier function, and
evaluating the degree of recovery and enhancement of barrier
function, but because of the lack of appropriate factors allowing
convenient evaluation with small specimens, it has been a goal to
identify such factors.
[0005] Almost all amino acids are known to be classified according
to their enantiomeric absolute configuration, named as L-form and
D-form, with the amino acids in living organisms being mainly the
L-form, while D-amino acids have been thought to be found in a very
limited number of biological components such as bacterial
peptidoglycans. However, the results of recent research have
demonstrated that various D-amino acids are to be found not only in
microorganisms but also in plants and mammals, either in free form
or as the amino acid residues composing proteins, and that they
exhibit various types of physiological function. The firstly found
free D-amino acids in mammals were D-serine and D-aspartic acid.
D-serine is localized in the cerebrum and hippocampus and functions
as an NMDA receptor co-agonist, and it has been found to play a
role in excitatory neurotransmission control (NPL 1). Also,
D-aspartic acid is localized in the testis and pineal body and has
been found to contribute to control of hormone secretion. Results
of recent research on D-amino acids have also further demonstrated
that D-serine, D-aspartic acid, D-alanine, D-glutamic acid and
D-proline are present in the dermis and epidermis, and are reduced
with aging (NPL 2). D-serine is the D-amino acid with the highest
content in the epidermis and stratum corneum, and while one role
played by D-serine in the skin has been found to be alleviation of
ultraviolet damage in dermal fibroblasts (PTL 2), its role in the
epidermis where it is present in a higher content remains
unknown.
[0006] Amino acid racemases are known as enzymes involved in
production of D-amino acids, and they are classified into enzymes
dependent on pyridoxalphosphoric acid (PLP) and racemases that do
not require cofactors. Among reports that D-amino acids are present
in eukaryotic cells including those of mammals it has been reported
that PLP-dependent serine racemase is present in mammals (NPL 3),
but it has not yet been confirmed whether or not aspartic acid
racemase is present with racemase activity in mammals. Since
D-serine is localized in the cerebrum and hippocampus, expression
of serine racemase in the brains of mammals including humans has
been confirmed, but there have been almost no reports of its
expression in other tissues (NPL 3).
CITATION LIST
Patent Literature
[0007] [PTL 1] Japanese Unexamined Patent Publication No.
2012-92032 [0008] [PTL 2] WO2011/030903
Non-Patent Literature
[0008] [0009] [NPL 1] S. H. Snyder, et al., NeuroChem Res 25, 553
(2000) [0010] [NPL 2] Y. Tojo, Food Style 21, 2013, August, (Vol.
17, No. 8) [0011] [NPL 3] Molecular Brain Research, Vol. 125, pp.
96-104, 2004 [0012] [NPL 4] Overview of experimental protocols for
development of functional cosmetic materials, CMC Publishing, 2010,
p. 214-216
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0013] There has been interest in increasing skin barrier function
by increasing intercellular lipid levels and ordering their
arrangement. On the other hand, in order to enhance and repair skin
barrier function, increasing the number of healthy stratum corneum
layers is thought to be an effective approach in view of increasing
physiological or structural skin barrier function. However, no
drugs with such effects have been known, and as mentioned above, it
has been difficult to discover such drugs by screening.
Accordingly, it has been desired to develop a method for screening
drugs having effects of increasing physiological or structural skin
barrier function.
Means for Solving the Problems
[0014] As a result of diligent research on D-serine whose function
in skin has not been known, the present inventors have discovered
that D-serine contributes to skin barrier function. Based on this
knowledge, it has become possible to provide a method for screening
drugs having effects of increasing skin barrier function by using
D-serine levels, as well as levels of expression and activity of
serine racemase that produces D-serine from L-serine in
keratinocytes as an indicator, and also to evaluate skin barrier
function enhancement in a convenient and stable manner with low
burden on subjects, whereupon the present invention has been
completed. By using the screening method, it has become possible to
screen for drugs that enhance skin barrier function.
[0015] Specifically, the present inventors have completed the
following invention.
[0016] [1] A method for screening a skin barrier function enhancing
agent, wherein an activity or expression level of serine racemase
and/or D-serine level in keratinocytes is used as an indicator.
[0017] [2] The screening method according to [1], comprising:
[0018] adding a candidate drug to keratinocytes;
[0019] measuring the activity or expression level of serine
racemase and/or the D-serine level in the keratinocytes; and
[0020] determining the skin barrier function-enhancing effect of
the candidate drug based on the expression level or activity of
serine racemase and/or the D-serine level.
[0021] [3] The screening method according to [2], further
comprising a step of inducing differentiation of the
keratinocytes.
[0022] [4] The screening method according to [3], wherein the
screening method is conducted in the differentiation-induced
keratinocytes.
[0023] [5] The screening method according to any one of [1] to [4],
wherein the measurement of the serine racemase expression level is
carried out by measuring the amount of serine racemase mRNA or
protein.
[0024] [6] The screening method according to any one of [1] to [4],
wherein the measurement of serine racemase activity is carried out
by measuring the substrate conversion efficiency or measuring the
amount of D-amino acid product.
[0025] [7] A serine racemase activating agent comprising one or
more substances selected from the group consisting of hydrolyzed
oat protein, Lempuyang extract, and Elephantopus mollis extract as
an active ingredient, which is obtained by the screening method
according to any one of [1] to [6].
[0026] [8] A method for evaluating the skin barrier function,
wherein an activity or expression level of serine racemase and/or
D-serine level from a skin sample isolated from human skin is used
as an indicator.
[0027] [9] The skin barrier function evaluation method according to
[8], comprising:
[0028] measuring the activity or expression level of serine
racemase and/or D-serine level in a skin sample isolated from a
subject, and
[0029] determining the skin barrier function of the subject from
the activity or expression level of serine racemase and/or D-serine
level.
[0030] [10] The skin barrier function evaluation method according
to [8] or [9], wherein measurement of the serine racemase
expression level is carried out by measuring the amounts of serine
racemase mRNA or protein.
[0031] [11] The method according to [8] or [9], wherein the
measurement of serine racemase activity is carried out by measuring
the substrate conversion efficiency by serine racemase or the
amount of D-amino acid product.
Effect of the Invention
[0032] It is possible to select drugs that can improve or enhance
skin barrier function by using the screening method of the
invention. In addition, the skin barrier function evaluation method
of the invention allows determining skin barrier function at the
cellular level or tissue level, or at the biochemical level.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1A shows a comparison of free L-serine levels in skin
in a high-TEWL group and a low-TEWL group. FIG. 1B shows a
comparison of free D-serine levels in skin in a high-TEWL group and
a low-TEWL group.
[0034] FIGS. 2A and 2B are chromatograms for detection of
intracellular D-serine before and after differentiation-inducing
stimulation of cultured keratinocytes.
[0035] FIG. 3A is a graph showing increase in free D-serine levels
by hydrolyzed oat protein solution, which is one of candidate
drugs. FIG. 3B is a graph showing increase in serine racemase
expression by hydrolyzed oat protein solution, which is one of
candidate drugs.
BEST MODE FOR CARRYING OUT THE INVENTION
[0036] The present invention relates to a method for screening skin
barrier function enhancing agents, using an indicator, or a
combination of two or more indicators among serine racemase
expression level, activity and D-serine level in keratinocytes.
[0037] It is possible to obtain drugs having skin barrier function
enhancing effects by using the screening method of the present
invention. Here, "skin barrier function" means the function of the
skin that retains moisture and prevents infiltration of foreign
matter from the exterior, and the function is performed by the
epidermis and especially by the stratum corneum. The skin barrier
function can be measured by transepidermal water loss (TEWL), with
higher moisture evaporation considered to be a lower skin barrier
function.
[0038] Enhancement of skin barrier function can be achieved, for
example but not limited to, by increasing the number of layers of
the stratum corneum, maturing the cornified envelope in the stratum
corneum or increasing intercellular lipids, such as cholesterol and
ceramide. Thus, while it is not intended to be constrained by
theory, it is conjectured that applying a drug selected by the
screening method of the invention onto skin can enhance serine
racemase expression or activity, or increase D-serine levels,
resulting in an effect of an increased number of layers of the
stratum corneum, thereby enhancing the skin barrier function.
[0039] A candidate drug provided to the screening method of the
invention can be any compounds, such as a compound obtained from a
combinatorial library, or a mixture or extract. Examples of
candidate drugs that may be used include libraries of compounds,
mixtures, or extracts of food materials, cosmetic materials or
pharmaceutical materials. The drugs considered to have skin barrier
function enhancing effects according to the present invention can
be applied in foods such as functional foods and nutritious foods,
cosmetics, pharmaceuticals, or quasi drugs. Examples of cosmetics
in which they may be applied include, for example but not limited
to, cosmetic waters, creams, latexes, gels, essences, ointments,
packs, bath additives, body soaps, shampoos, rinses, foundations
and the like. More preferably, they are applied to cosmetics for
sensitive skin, such as cosmetic waters, creams, latexes, essences
and the like. A pharmaceutical or quasi drug may be in the form of
any of various ointments or creams for transdermal administration,
or in a form for oral administration.
[0040] In the screening method of the invention, serine racemase
expression level or activity and/or D-serine level in
keratinocytes, are used as an indicator. Use as an indicator means
that the serine racemase expression level or activity, and/or
D-serine level, is the factor to be considered. Thus, when a
candidate drug is added, the screening method of the invention
encompasses selection of a drug having a skin barrier
function-enhancing effect based on serine racemase expression level
or activity, and/or D-serine level as the judgment criteria.
[0041] Keratinocytes are cells constituting approximately 95% of
the epidermis. Keratinocyte stem cells are present in the basal
lamina of the epidermis in the body, and they migrate to the
outside as they mature, thereby forming the stratum spinosum,
granular layer and stratum corneum. Keratinocytes change their
characteristics as they mature. The cells in the stratum spinosum
or granular layer become flattened, lipids such as ceramides are
released into the intercellular space, and then enucleation is
occurred in the stratum spinosum of the outermost layer. This
maturation process can be considered differentiation of
keratinocytes. The enucleated cells lose their cytomorphology and
become superposed, thereby forming the stratum corneum, and are
eventually shed off as scales from the outermost layer.
[0042] The cultured keratinocytes to be used for the invention may
be cells obtained from the epidermal basal lamina, stratum
spinosum, granular layer or stratum corneum, or cells that have
been induced to differentiate from stem cells such as skin
epithelial stem cells or pluripotent stem cells, for example, ES
cells, iPS cells, EG cells, etc. Cells obtained from the epidermis
and cultured may be primary cultured cells, subcultured cells, or
even cancerized or immortalized cells. The cultured keratinocytes
to be used for the invention may also be an established
keratinocyte line derived from a human or animal. Such keratinocyte
cell lines can be obtained from authorized institutions or
distributors.
[0043] The cultured product may refer to the desired cells alone,
or it may also contain other cells or it may be composed of the
cells and the culture medium. Thus, cultured keratinocytes may
refer to the keratinocytes alone, or to a combination of the
keratinocytes with other cells, or to culture medium with the
keratinocytes alone or with the keratinocytes and other cells. Such
a cultured product may include a monolayer cultured product, mixed
cultured product or three-dimensional cultured product. The culture
medium in which the keratinocytes are cultured may include any
desired culture medium so long as it allows to culture
keratinocytes, for example not limited to, HuMedia-KB2 (Kurabo
Industries, Ltd.) or Keratinocyte-SFM (Invitrogen Corp.) medium
with addition of various additives may be used. The culturing
conditions will usually be at 37.degree. C. in the presence of 5%
CO.sub.2, with variation in a range that permits proliferation of
keratinocytes. The culture medium is preferably in an
L-serine-enriched state, from the viewpoint of using D-serine
abundance as an index of serine racemase activity. In most cases,
D-amino acids will not be intentionally added to the culture
medium, and the abundance of L-serine with respect to D-serine in
the culture medium will be at least 1.1-fold, more preferably
10-fold and even more preferably 50-fold or greater. For example,
culture medium (KGM culture medium) obtained by adding an
HuMedia-KG proliferating additive set to HuMedia-KB2 (Kurabo
Industries, Ltd.) has the 100-fold or greater abundance of L-serine
with respect to D-serine.
[0044] The keratinocytes cultured product has been cultured after
seeding, and the keratinocytes cultured product being about 50%
confluency toconfluent can be subjected to experiment. The
confluency is preferably 70% or greater and even more preferably
80% or greater, from the viewpoint of inducing differentiation. The
process for adding a candidate drug to the cultured keratinocytes
may involve exchanging the culture medium for the cultured
keratinocytes with a culture medium containing the candidate drug,
or adding the candidate drug, either directly or as a diluted
solution, to the cultured product containing the keratinocytes and
the culture medium.
[0045] Serine racemase is a racemase that is dependent on
pyridoxal-5' phosphate (PLP), a coenzyme of vitamin B6. While it is
not intended to be constrained by theory, serine racemase is an
enzyme capable of conversion between L-serine and D-serine via
production of an anionic intermediate, by withdrawal of the
.alpha.-hydrogen from serine. In the conversion reaction between
L-serine and D-serine, there is no change in enthalpy before and
after the reaction, and the reaction is driven by entropy.
Therefore, L-serine and D-serine are equivalent in the equilibrium
state. Since the abundance of L-serine is greater than D-serine in
the body, the presence of serine racemase converts L-serine in the
body to D-serine. Since the L-form is usually more abundant in
culture medium even under culturing conditions, the presence of
serine racemase similarly converts L-serine to D-serine. According
to the invention, the racemase can be identical to the racemase
found to be expressed in the brain according to NPL 3, or a homolog
or ortholog thereof. Thus, it can be amplified by a primer pair
used in that publication, and is detectable by the racemase
antibody described in the same publication. Serine racemase can be
identified by a person skilled in the art according to animal
species, from the web site of an authorized institution such as
NCBI.
[0046] According to one aspect of the invention, serine racemase
activity in keratinocytes can be used as an indicator for
evaluation of skin barrier function or for screening of skin
barrier function enhancing agents. Serine racemase activity can
generally be based on the amount of D-serine produced by conversion
of L-serine in the culture medium, when a substance acting as the
substrate for the enzyme is not added, or it may be based on the
total amount of other D-amino acids including D-serine. Also,
addition of a substance other than serine that can serve as a
substrate for serine racemase may be carried out to measure the
amount of product or measure the conversion efficiency, based on
conversion of the additive. Since serine racemase converts excess
optical isomer to the other optical isomers until the D-form and
L-form ratio become 50:50, it is of course possible to add the
D-form for activity measurement. In this case, evaluation of enzyme
activity can be accomplished even by measuring the increase in
L-serine produced by conversion. If a derivative of cycloserine or
serine (such as the N-methylated form, acetylated form or
phosphorylated form) is also added, it is possible to evaluate the
enzyme activity by examining the conversion efficiency to the
corresponding optical isomer. When serine racemase activity is to
be measured based on the D-serine level, it may be determined by
the abundance of D-serine in a skin sample isolated from a subject,
or in cultured keratinocytes, i.e. in a culture medium, cells or
both, or it may be determined by an enzymatic parameter determined
based on the change in the abundance of D-serine in a skin sample
or in cultured keratinocytes. This method is applicable to all of
the aforementioned substances that can act as enzyme substrates.
The enzymatic parameter representing serine racemase enzyme
activity may be obtained by determining the V.sub.max or K.sub.m
values.
[0047] According to another aspect of the present invention, the
D-serine level in keratinocytes can be used as an indicator for
evaluation of skin barrier function or for screening of skin
barrier function enhancing agents. The D-serine level may be
measured in a skin sample isolated from a subject, or in cultured
keratinocytes, i.e. in a culture medium, cells or both. The method
of measuring the D-serine level may be carried out using a known
method. For example, it may be carried out by an HPLC method using
an optical isomer separating column, or a gas chromatography,
electrophoresis or enzyme method. When measurement of the serine
racemase activity is carried out by measuring the D-serine level,
L-serine may be added to the cultured keratinocytes to increase the
D-serine level. When serine racemase catalyzes conversion reaction
between L-serine and D-serine, the enthalpy before and after the
reaction does not change, and the reaction is driven by entropy.
Therefore addition of L-serine can increase the D-serine level in
proportion to the serine racemase activity, and therefore
measurement of the D-serine level becomes easier.
[0048] According to another aspect, serine racemase expression
level can be used as an indicator for evaluation of skin barrier
function or for screening of skin barrier function enhancing
agents. The serine racemase expression level can be determined by
measuring serine racemase protein by an immunological method using
anti-serine racemase antibody. The immunological method can be
carried out by Western blotting, fluorescent immunostaining or
ELISA. The anti-serine racemase antibody used may be monoclonal
antibody or polyclonal antibody, and it may be antibody collected
by immunizing an experimental animal such as a rabbit or mouse with
serine racemase protein or antigen peptide.
[0049] It can also be accomplished by determining the serine
racemase expression level based on the amount of serine racemase
mRNA in cells. The mRNA may be measured by any desired method, and
for example, it can be measured based on a quantitative PCR method.
A quantitative PCR method is usually conducted as follows, with the
understanding that this is not limitative. The mRNA is extracted
from collected cells, and cDNA is prepared using polyT primer and
reverse transcriptase. The prepared cDNA may be subjected to the
SYBR green method or fluorogenic probe method to quantify the
amount of mRNA in the cells.
[0050] More specifically, the screening method of the invention may
comprise the following steps:
[0051] adding a candidate drug to keratinocytes,
[0052] measuring the expression level or activity of serine
racemase and/or the D-serine level in keratinocytes, and
[0053] determining the skin barrier function-enhancing effect of
the candidate drug based on the expression level or activity of
serine racemase and/or the D-serine level. The screening method of
the invention may further comprise a step of inducing
differentiation of keratinocytes.
[0054] The differentiation inducing step is carried out by
subjecting keratinocytes to differentiation-inducing stimulation.
Subjecting keratinocytes to differentiation-inducing stimulation
results in cellular flattening, increase in intracellular fibers or
granules, indistinct intercellular spaces, superpositioning
(especially with monolayer cultures), and finally resulting in the
morphological change of enucleation, or changes in cells that
result in production of or changes in proteins such as keratin 1,
keratin 10, involucrin or transglutaminase activation (see Nippi
Kaishi, 90(12), 1089-1101, http://drmtl.org/data/090121089.pdf,
Drug News Perspect 2004, 17(2) p 117). The differentiation-inducing
stimulation may be any desired stimulation that can produce the
aforementioned differentiation of keratinocytes, and may include,
for example, stimulation of calcium ion that increases the calcium
ion concentration, stimulation with phorbol-12-myristate-13-acetate
(Hawley-Nelson P, Stanley J R et al, Exp Cell Res, 137: 155-167,
1982), physical stimulation by voltage or gas phase exposure, or
stimulation with a biological solution. For stimulation with
calcium ion, a calcium salt or its diluted solution may be added to
a concentration of 0.1 mM to 10 mM as the final concentration of
calcium ion, or the culture medium may be exchanged with medium
already adjusted to a final concentration of calcium ion. The
calcium salt used includes, for example, calcium chloride, calcium
hydrogencarbonate, calcium carbonate, calcium nitrate or calcium
acetate, etc. The upper limit for the final calcium ion
concentration is preferably 5 mM and even more preferably 2 mM,
from the viewpoint of not adversely affecting the cell culture.
From the viewpoint of promoting the induced differentiation, the
lower limit for the concentration is preferably 0.5 mM and more
preferably 1.0 mM.
[0055] The differentiation-inducing step and the candidate drug
addition step may be carried out simultaneously, the candidate drug
addition step may be carried out after the differentiation-inducing
step, or conversely the differentiation-inducing step may be
carried out after the candidate drug addition step. While it is not
intended to be limited to theory, the timing for inducing
differentiation and adding candidate drugs can be varied depending
on the action mechanism desired for the candidate drug. For
example, from the viewpoint of examining antagonism of drugs with
differentiation-inducing stimulation substances, the addition step
is preferably carried out either simultaneously with or before the
stimulation step. Also, from the viewpoint of promoting or
inhibiting cellular changes (morphological changes, and expression
of various intracellular factors) after differentiation has been
induced, the addition step is preferably carried out simultaneously
with or after the stimulating step, and from the viewpoint of
illuminating mechanisms such as exploring mechanisms such as
pre-blocking of receptors on which differentiation-inducing
stimulation acts, the stimulating step is preferably carried out
after the addition step. When the candidate drug addition step and
the differentiation-inducing stimulation step are not carried out
simultaneously, a cell culturing step of several minutes to several
hours may be included between the addition step and the stimulation
step.
[0056] After differentiation-inducing stimulation and candidate
drug addition, a cell culturing step may be further included before
the step of measuring the serine racemase expression level or
activity and/or the D-serine level. The period for the cell
culturing step can be selected as desired depending on the type and
concentration of the differentiation-inducing agent used and the
type of keratinocytes, and culturing may be conducted for 6 hours
to 1 week, for example. From the viewpoint of adequately expressing
serine racemase, the minimum culturing period is preferably 12
hours and more preferably 1 day. On the other hand, the maximum
culturing period cannot be specified since it will differ depending
on the culturing method, such as monolayer culturing, multi-layered
culturing or three-dimensional culturing, but from the viewpoint of
maintaining normal cell culturing conditions it is preferably no
longer than one week and more preferably no longer than 3 days, for
monolayer culturing.
[0057] The screening method of the invention may further include a
damage-inducing step. The damage-inducing step may be inducement of
damage by physical or chemical stimulation of the cultured
keratinocytes, such as addition of a radical source such as
ultraviolet irradiation or an oxidizing agent, addition of a
surfactant, or exchange with oligotrophic medium. The keratinocytes
that have been damaged by the damage-inducing step may be expected
to have reduced serine racemase expression. Thus, in a screening
method in which a damage-inducing step is carried out after the
candidate drug addition step, if reduction in racemase expression
level or racemase activity and/or D-serine level is found to be
suppressed, the candidate drug can be used as a preventive drug
against damage to skin barrier function. On the other hand, in a
screening method in which a candidate drug addition step is carried
out after a damage-inducing step, if reduced racemase expression
level or racemase activity and/or D-serine level is found to be
increased, the candidate drug can be used as a restoring,
ameliorating or curative agent for skin barrier function. In a
screening method where damage is not induced, a candidate drug that
increases racemase expression level or racemase activity, and/or
D-serine level, can be considered to be an enhancer of skin barrier
function.
[0058] As a result of carrying out the screening method of the
present invention, hydrolyzed oat protein, Lempuyang extract,
Elephantopus mollis extract can be selected as an agent enhancing
skin barrier function. However, such an agent is not limited to
extract derived from Lempuyang and Elephantopus mollis, extract
derived from related species has the skin barrier function
enhancing effect in a similar way. The skin barrier function
enhancing agent of the present invention include extract of a plant
belonging to the genus Zingiber of Zingiberaceae family and a plant
belonging to the Elephamtopus genus of Compositae family.
Therefore, a cosmetic product exerting skin barrier function
enhancing effect can be prepared by containing these substances in
a cosmetic product.
[0059] The hydrolyzed oat protein used in the present invention is
a hydrolyzate of protein obtained from oat (Avena sativa L.). While
the protein of oat is extracted, for example, from seeds, leaves,
roots, and from bran, the seeds are particularly preferred. The
oat, which was immediately dried and ground after harvest, are
preferred. It may be dried under the sun, or may be dried by using
a drying machine that is normally used. The protein is hydrolyzed
by the acid or enzyme treatment in the process of extraction or
after extraction. Oats is a plant that is grown for food from West
Asia to Europe and North America. The extraction solvent used in
the present invention can be any solvent usually used for
extraction. In particular, an organic solvent including alcohols
such as methanol, ethanol, water-containing alcohols, acetone,
ethyl acetate ester can be used for extraction alone or in
combination. It is possible to perform the extraction with
water.
[0060] The amount of the hydrolyzed oat protein of the present
invention can be arbitrarily selected by a person skilled in the
art within the scope exerting an effect. For example, the amount of
the extract constitutes, as a dry composition, 0.0005-20.0 wt % of
the total amount of the external formula The upper limit of the
amount is preferably less than 10 wt % by weight or less, and more
preferably 5 wt % or less from the viewpoint of exerting an effect
and preparing a formulation. The lower limit of the amount is
preferably 0.0001 wt % or more, more preferably 0.0005 wt % or more
in view of exerting a sufficient skin barrier function enhancing
effect.
[0061] Among plants belonging to the genus Zingiber of
Zingiberaceae family, Lempuyang (Zingiber aromaticum Mal.) is
preferable. Lempuyang is a plant growing dry grassland and pasture
in particular in Indonesia. The extract used in the present
invention is prepared by immersing foliage, stem including
rhizomes, fruits, etc., of the plant and the whole plant in an
extract solvent, optionally heating the mixture to reflux, then
being subjected to filtration and concentration. The extraction
solvent used in the present invention can be any solvent usually
used for extraction. In particular, an organic solvent including
alcohols such as methanol, ethanol, water-containing alcohols,
acetone, ethyl acetate ester can be used for extraction alone or in
combination. It is possible to perform the extraction with
water.
[0062] The amount of the extract of a plant belonging to the genus
Zingiber of Zingiberaceae family can be arbitrarily selected by a
person skilled in the art within the scope exerting an effect. For
example, the amount of the extract constitutes, as a dry
composition, 0.0005-20.0 wt % of the total amount of the external
formula The upper limit of the amount is preferably less than 10 wt
% by weight or less, and more preferably 5 wt % or less from the
viewpoint of exerting an effect and preparing a formulation. The
lower limit of the amount is preferably 0.0001 wt % or more, more
preferably 0.0005% wt % or more in view of exerting a sufficient
skin barrier function enhancing effect.
[0063] Among a plant belonging to the genus Elephamtopus of
Compositae family, Elephantopus mollis is preferable. Elephantopus
mollis is an indigenous plant in Venezuela of South America, and
has been widely naturalized in tropical Asia. The extract of a
plant belonging to the genus Elephamtopus of Compositae family is
prepared by immersing Leaves, stems, flowers, bark, seeds or fruit,
etc., of the plant and the whole plant in an extract solvent,
optionally heating the mixture to reflux, then being subjected to
filtration and concentration. The extraction solvent used in the
present invention can be any solvent usually used for extraction.
In particular, an organic solvent including alcohols such as
methanol, ethanol, water-containing alcohols, acetone, ethyl
acetate ester can be used for extraction alone or in combination.
It is possible to perform the extraction with water.
[0064] The amount of the extract of a plant belonging to the genus
Elephamtopus of Compositae family can be arbitrarily selected by a
person skilled in the art within the scope exerting an effect. For
example, the amount of the extract constitutes, as a dry
composition, 0.0005-20.0 wt % of the total amount of the external
formula The upper limit of the amount is preferably less than 10 wt
% by weight or less, and more preferably 5 wt % or less from the
viewpoint of exerting an effect and preparing a formulation. The
lower limit of the amount is preferably 0.0001 wt % or more, more
preferably 0.0005% wt % or more in view of exerting a sufficient
skin barrier function enhancing effect.
[0065] In a step of determining the skin barrier function-enhancing
function of a candidate drug based on serine racemase expression
level or activity, or D-serine level, it is possible to determine
it based on the measured serine racemase expression level or
activity and/or D-serine level using a preset table showing the
relationship between expression level or activity and/or D-serine
level and barrier function-enhancing function. Such a table can be
prepared using racemase expression level or activity and/or
D-serine level measured by a similar experiment without the
candidate drug, as a control, or using racemase expression level or
activity and/or D-serine level measured by a similar experiment
using a control drug known to increase serine racemase expression
level or activity and/or D-serine level. According to a different
aspect, the skin barrier function-enhancing action of a candidate
drug can be determined by setting a predetermined threshold value
based on comparison with a control, and determining whether or not
the effect is higher than the threshold value by a statistically
significant difference. A person skilled in the art can
appropriately set the threshold value according to the skin barrier
function-enhancing effect that is desired. Such a threshold value
may be a threshold value set to an arbitrary factor with respect to
serine racemase expression level or activity and/or D-serine level
for a control where the drug has not been added, and for example,
the value may be set to a factor of 1.1, for example, by a
statistically significant difference and marginal significant
difference. A statistically significant difference is p<0.05,
and a marginal significant difference is p<0.1. Also, according
to yet a different mode, it may be determined that a skin barrier
function-enhancing effect is exhibited in the case of high
expression level or activity compared to the racemase expression
level or activity and/or D-serine level measured by conducting a
similar experiment without the candidate drug, as a control, in
which case it can be determined that higher expression level or
activity and/or D-serine level is a greater skin barrier
function-enhancing effect.
[0066] According to yet another aspect, the invention relates to a
method of evaluating, judging and discriminating skin barrier
function using serine racemase expression level or activity and/or
D-serine level as an indicator. Such evaluation, judgment or
discrimination can be made by measuring D-serine content, serine
racemase activity or serine racemase expression level for a skin
sample such as a stratum corneum sample obtained by tape stripping,
for example, from a subject. The method of evaluating, judging or
discriminating skin barrier function will usually be carried out by
measuring TEWL using a Vapometer. However, TEWL is dependent on the
state of the skin and its numerical values vary depending on
rinsing and abrasion, while in skin disease patients there is no
definite correlation between the numerical values and skin health.
The evaluation, judgment and discrimination method of the invention
uses serine racemase activity or expression level and/or D-serine
level as an indicator to allow measurement of the original
cellular-level skin barrier function of skin.
[0067] Also, since the evaluation method of the invention
determines the normalcy of skin barrier function on the cellular
level, it allows prediction of future skin barrier function rather
than current skin barrier function. The evaluation, judgment or
discrimination of skin barrier function can be made using a table
or threshold value representing the relationship between a
previously set serine racemase expression level or activity and/or
D-serine level, and barrier function-enhancing effect. Such a table
or threshold value can be set based on expression level or activity
and/or D-serine level obtained for a skin sample obtained and
isolated from subject groups with healthy skin, subject groups with
roughened skin, and from age-classified subject groups.
[0068] The present invention will now be explained in greater
detail by the following examples. However, the invention is in no
way limited by the examples.
EXAMPLES
Example 1
Verification of Relationship Between D-Serine Content and Barrier
Function in Stratum Corneum
[0069] The subjects were 57 volunteers having healthy test sites,
and the test sites wetted by rinsing after cleaning by a prescribed
method were allowed to stand for 30 minutes at constant
temperature, constant humidity conditions (room temperature:
22.degree. C., humidity: 45%). Next, the transepidermal water loss
(TEWL) was measured with a Vapometer (Delfin Co.). Measurement was
performed 3 times and the average value was subsequently used for
analysis. Next, the stratum corneum at the TEWL-measured site was
stripped twice using adhesive tape and the second was used for
extraction of amino acids in a 95% methanol aqueous solution. The
optical isomers of the extracted amino acids were analyzed by a
reported method (reference: Yurika Miyoshi et al., Journal of
Chromatography B, 877 (2009) 2506-2512). The results are summarized
below. The extracted amino acids were subjected to fluorescent
derivatization with 4-fluoro-7-nitro-2,1,3-benzooxadiazole (NBD-F)
in a borate buffer (pH 8.0). After this derivatization, pH of the
solution was adjusted to acidic conditions by adding
trifluoroacetic acid. The derivatives were subjected
two-dimensional Micro HPLC (Shiseido Corp.). For the first
dimension there was used a micro monolithic ODS column (inner
diameter: 0.53 mm, full lengths: 500, 750, 1000 mm, Shiseido
Corp.), and for the second dimension there was used an optical
resolution enantio-selective column (inner diameter: 1.5 mm, full
length: 250 mm, mobile phase conditions were optimized for each
amino acid). The NBD-amino acids were detected by fluorescence at
530 nm (excitation wavelength of 470 nm). The results are shown in
Table 1 and FIG. 1.
TABLE-US-00001 TABLE 1 High TEWL group Low TEWL group (=low barrier
group) (=high barrier group) D-Ser L-Ser D-Ser L-Ser (fmol/ (fmol/
(fmol/ (fmol/ in- injec- injec- injec- n TEWL jection) tion) TEWL
tion) tion) Mean 10 69 97633 6 106 123496 SE 0.23 11 16503 0.15 16
19546 p-value in 0.013 0.146 student's t-test
[0070] In order to verify the relationship between D-serine (D-Ser)
content and skin barrier function in the stratum corneum, the
subjects were ordered according to TEWL value, and the D-serine
contents in the stratum corneum were compared between the top 17
(inferior barrier function group) and bottom 17 (superior barrier
function group). The significant difference between the two groups
was verified by a non-paired Student's t-test. The results
demonstrated that humans with high skin barrier function had
significantly high D-serine contents. On the other hand, results of
comparison for L-serine indicated a tendency toward lower L-serine
content in the inferior barrier function group and higher L-serine
content in the superior barrier function group, although the
difference was not significant. Thus, it may be concluded that the
high D-serine content in the superior barrier function group was
not due to the amount of L-serine as the precursor, but rather to
racemase expression and activity.
Example 2
Variation in D-Serine Content with Induced Differentiation of
Keratinocytes
Cell Culturing and Drug Preparation
[0071] Normal human keratinocytes were seeded in a 24 well
multiplate to a cell density of 2.5.times.10.sup.4 cells/well, and
cultured in KGM culture medium (Kurabo Industries, Ltd.) under
conditions of 37.degree. C., 5% CO.sub.2. After 3 days, the medium
was exchanged with KGM culture medium to which 1.8 mM calcium
chloride and 10 mM L-serine had been added (test group), or KGM
culture medium to which 10 mM L-serine alone had been added
(control group), and culturing was continued for another 2
days.
HPLC Sample Preparation and Free D-Serine Analysis by HPLC.
[0072] After rinsing cells with PBS, 500 .mu.L of a 5%
trichloroacetic acid aqueous solution was added, the cells were
thoroughly dispersed and recovered, and ultrasonic treatment was
performed for 30 minutes on ice, after which centrifugal separation
was performed to obtain a supernatant. The amino acids in the
supernatant were extracted by addition of a 20-fold amount of
methanol. The optical isomers of the extracted amino acids were
analyzed by a reported method (reference: Yurika Miyoshi et al.,
Journal of Chromatography B, 877 (2009) 2506-2512). The results are
summarized below. The extracted amino acids were subjected to
fluorescent derivatization with
4-fluoro-7-nitro-2,1,3-benzooxadiazole (NBD-F) in a borate buffer
(pH 8.0). After this derivatization, pH of the solution was
adjusted to acidic conditions by adding trifluoroacetic acid. The
derivatives were subjected to two-dimensional Micro HPLC (Shiseido
Corp.). For the first dimension there was used a micro monolithic
ODS column (inner diameter: 0.53 mm, full length: 750 mm, Shiseido
Corp.), and for the second dimensional optical resolution, there
was used an optical resolution enantio-selective column inner
diameter: 1.5 mm, full length: 250 mm, mobile phase conditions were
optimized for each amino acid). The NBD-amino acids were detected
by fluorescence at 530 nm (excitation wavelength of 470 nm). The
results for the test group and control group are shown in FIG.
2.
Example 3
Screening of Candidate Drugs
Cell Culturing and Drug Preparation
[0073] Normal human keratinocytes were seeded in a 24 well
multiplate to a cell density of 2.5.times.10.sup.4 cells/well, and
cultured in KGM culture medium (Kurabo Industries, Ltd.) under
conditions of 37.degree. C., 5% CO.sub.2. After 3 days, the medium
was exchanged with KGM culture medium containing 1.8 mM calcium
chloride, 10 mM L-serine and the candidate drug diluted solution,
and culturing was continued for another 2 days. Seven drugs were
used as candidate drugs, of which one was a 0.5% hydrolyzed oat
protein solution.
HPLC Sample Preparation and Free D-Serine Analysis by HPLC.
[0074] After rinsing cells with PBS, 500 .mu.L of a 5%
trichloroacetic acid aqueous solution was added, the cells were
thoroughly dispersed and recovered, and ultrasonic treatment was
performed for 30 minutes on ice, after which centrifugal separation
was performed to obtain a supernatant. The amino acids in the
supernatant were extracted by addition of a 20-fold amount of
methanol. The optical isomers of the extracted amino acids were
analyzed by a reported method (reference: Yurika Miyoshi et al.,
Journal of Chromatography B, 877 (2009) 2506-2512). The results are
summarized below. The extracted amino acids were subjected to
fluorescent derivatization with
4-fluoro-7-nitro-2,1,3-benzooxadiazole (NBD-F) in a borate buffer
(pH 8.0). After this derivatization, pH of the solution was
adjusted to acidic conditions by adding trifluoroacetic acid. The
derivatives were subjected to two-dimensional Micro HPLC (Shiseido
Corp.). For the first dimension there was used a micro monolithic
ODS column (inner diameter: 0.53 mm, full length: 750 mm, Shiseido
Corp.), and for the second dimensional optical resolution, there
was used an optical resolution enantio-selective column (inner
diameter: 1.5 mm, full length: 250 mm, mobile phase conditions were
optimized for each amino acid). The NBD-amino acids were detected
by fluorescence at 530 nm (excitation wavelength of 470 nm). The
results are shown in Table 2 and FIG. 3A below.
Quantitative PCR (RT-PCR)
[0075] After rinsing cells with PBS, MagNA Pure LC (Roche
Diagnostic Corp.) was used to extract the mRNA from the cells.
Next, a reverse transcriptase SuperScriptVILO (Invitrogen Corp.)
kit was used to synthesize cDNA. The cDNA was used as template for
real-time PCR using fluorescent dye CyberGreen with a LightCycler
(Roche Diagnostic Corp.). The PCR reaction was enzyme activation at
95.degree. C. for 10 minutes followed by amplification reaction at
95.degree. C. for 15 seconds, 60.degree. C. for 10 seconds and
72.degree. C. for 10 seconds, repeated 30 times. The gene
expression level was calculated as a relative value from the number
of cycles until a unit PCR product was obtained. RT-PCR was
conducted with the G3PDH (glyceraldehyde-3-phosphate) gene as the
internal standard in addition to the serine racemase gene, and the
drug evaluation was conducted by correlating the relative
expression level of serine racemase with the relative expression
level of G3PDH. The primers selected for use in RT-PCR were those
described in NPL 3 and NPL 4. The results are shown in Table 2 and
FIG. 3B below.
TABLE-US-00002 TABLE 2 PCR results SR D-Serine content SR
expression p value SR content SR expression SD (VS SR content SD p
value expression/ (% control L- (% control control) (% control (%
control (VS control) G3PDH Ser(+)) L-Ser(+)) Student's t L-Ser(+))
L-Ser(+)) Student's t Control 100.00 3.50 100.00 19.40 Oat protein
151.94 37.30 0.074 119.09 3.43 0.063
[0076] Of the candidate drugs supplied for this screening, the
hydrolyzed oat protein solution promoted serine racemase expression
in differentiation-induced keratinocytes. It was also shown that
hydrolyzed oat protein solution increases the D-serine content in
differentiation-induced keratinocytes. Based on these results,
hydrolyzed oat protein solution can be selected as an effective
drug for enhancing skin barrier function.
Example 4
Screening of Candidate Drugs
Cell Culturing and Drug Preparation
[0077] Normal human keratinocytes were seeded in a 24 well
multiplate to a cell density of 2.5.times.10.sup.4 cells/well, and
cultured in KGM culture medium (Kurabo Industries, Ltd.) under
conditions of 37.degree. C., 5% CO.sub.2. After 3 days, the medium
was exchanged with KGM culture medium containing 1.8 mM calcium
chloride, 10 mM L-serine and the candidate drug diluted solution,
and culturing was continued for another 2 days. 12 drugs were used
as candidate drugs, in which 0.5% Lempuyang extract and 0.5%
Elephantopus mollis extract were included.
Quantitative PCR (RT-PCR)
[0078] After rinsing cells with PBS, MagNA Pure LC(Roche Diagnostic
Corp.) was used to extract the mRNA from the cells. Next, a reverse
transcriptase SuperScriptVILO (Invitrogen Corp.) kit was used to
synthesize cDNA. The cDNA was used as template for real-time PCR
using fluorescent dye CyberGreen with a LightCycler (Roche
Diagnostic Corp.). The PCR reaction was enzyme activation at
95.degree. C. for 10 minutes followed by amplification reaction at
95.degree. C. for 15 seconds, 60.degree. C. for 10 seconds and
72.degree. C. for 10 seconds, repeated 30 times. The gene
expression level was calculated as a relative value from the number
of cycles until a unit PCR product was obtained. RT-PCR was
conducted with the G3PDH (glyceraldehyde-3-phosphate) gene as the
internal standard in addition to the serine racemase gene, and the
drug evaluation was conducted by correlating the relative
expression level of serine racemase with the relative expression
level of G3PDH. The primers selected for use in RT-PCR were those
described in NPL 3 and NPL 4. The results are shown in Table 3
below.
TABLE-US-00003 TABLE 3 PCR results Serine Serine Racemase Serine
Racemase expression p value Racemase expression SD (VS expression/
(% control L- (% control control) G3PDH Ser(+)) L-Ser(+)) Student's
t Control 100.00 36.50 Lempuyang 170.02 36.18 0.068 extract
Elephantopus 173.07 15.90 0.011 mollis extract
[0079] Of the candidate drugs supplied for this screening,
Lempuyang extract and Elephantopus mollis extract promoted serine
racemase expression in differentiation-induced keratinocytes. Based
on this result, Lempuyang extract and Elephantopus mollis extract
can be selected as an effective drug for enhancing skin barrier
function.
* * * * *
References